@@ -11,7 +11,7 @@ $(LIBBPF_A):
 	$(Q)$(MAKE) -C $(LIBBPF_SRCS) O=$(LIBBPF_OUT)/ OUTPUT=$(LIBBPF_OUT)/ $(LIBBPF_OUT)/libbpf.a
 
 userprogs := bpfilter_umh
-bpfilter_umh-objs := main.o map-common.o codegen.o context.o match.o target.o
+bpfilter_umh-objs := main.o map-common.o codegen.o context.o match.o target.o rule.o
 bpfilter_umh-objs += xt_udp.o
 bpfilter_umh-userldlibs := $(LIBBPF_A) -lelf -lz
 userccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi -I $(srctree)/tools/lib

@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2021 Telegram FZ-LLC
+ */
+
+#define _GNU_SOURCE
+
+#include "rule.h"
+
+#include "../../include/uapi/linux/bpfilter.h"
+
+#include <linux/err.h>
+#include <linux/if_ether.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "codegen.h"
+#include "context.h"
+#include "match.h"
+
+static const struct bpfilter_ipt_target *
+ipt_entry_target(const struct bpfilter_ipt_entry *ipt_entry)
+{
+	return (const void *)ipt_entry + ipt_entry->target_offset;
+}
+
+static const struct bpfilter_ipt_match *ipt_entry_match(const struct bpfilter_ipt_entry *entry,
+							size_t offset)
+{
+	return (const void *)entry + offset;
+}
+
+static int ipt_entry_num_matches(const struct bpfilter_ipt_entry *ipt_entry)
+{
+	const struct bpfilter_ipt_match *ipt_match;
+	uint32_t offset = sizeof(*ipt_entry);
+	int num_matches = 0;
+
+	while (offset < ipt_entry->target_offset) {
+		ipt_match = ipt_entry_match(ipt_entry, offset);
+
+		if ((uintptr_t)ipt_match % __alignof__(struct bpfilter_ipt_match))
+			return -EINVAL;
+
+		if (ipt_entry->target_offset < offset + sizeof(*ipt_match))
+			return -EINVAL;
+
+		if (ipt_match->u.match_size < sizeof(*ipt_match))
+			return -EINVAL;
+
+		if (ipt_entry->target_offset < offset + ipt_match->u.match_size)
+			return -EINVAL;
+
+		++num_matches;
+		offset += ipt_match->u.match_size;
+	}
+
+	if (offset != ipt_entry->target_offset)
+		return -EINVAL;
+
+	return num_matches;
+}
+
+static int init_rule_matches(struct context *ctx, const struct bpfilter_ipt_entry *ipt_entry,
+			     struct rule *rule)
+{
+	const struct bpfilter_ipt_match *ipt_match;
+	uint32_t offset = sizeof(*ipt_entry);
+	struct match *match;
+	int err;
+
+	rule->matches = calloc(rule->num_matches, sizeof(rule->matches[0]));
+	if (!rule->matches)
+		return -ENOMEM;
+
+	match = rule->matches;
+	while (offset < ipt_entry->target_offset) {
+		ipt_match = ipt_entry_match(ipt_entry, offset);
+		err = init_match(ctx, ipt_match, match);
+		if (err) {
+			free(rule->matches);
+			rule->matches = NULL;
+			return err;
+		}
+
+		++match;
+		offset += ipt_match->u.match_size;
+	}
+
+	return 0;
+}
+
+static int check_ipt_entry_ip(const struct bpfilter_ipt_ip *ip)
+{
+	if (ip->flags & ~BPFILTER_IPT_F_MASK)
+		return -EINVAL;
+
+	if (ip->invflags & ~BPFILTER_IPT_INV_MASK)
+		return -EINVAL;
+
+	return 0;
+}
+
+bool rule_has_standard_target(const struct rule *rule)
+{
+	return rule->target.target_ops == &standard_target_ops;
+}
+
+bool is_rule_unconditional(const struct rule *rule)
+{
+	static const struct bpfilter_ipt_ip unconditional;
+
+	if (rule->num_matches)
+		return false;
+
+	return !memcmp(&rule->ipt_entry->ip, &unconditional, sizeof(unconditional));
+}
+
+int init_rule(struct context *ctx, const struct bpfilter_ipt_entry *ipt_entry, struct rule *rule)
+{
+	const struct bpfilter_ipt_target *ipt_target;
+	int err;
+
+	err = check_ipt_entry_ip(&ipt_entry->ip);
+	if (err)
+		return err;
+
+	if (ipt_entry->target_offset < sizeof(*ipt_entry))
+		return -EINVAL;
+
+	if (ipt_entry->next_offset < ipt_entry->target_offset + sizeof(*ipt_target))
+		return -EINVAL;
+
+	ipt_target = ipt_entry_target(ipt_entry);
+
+	if (ipt_target->u.target_size < sizeof(*ipt_target))
+		return -EINVAL;
+
+	if (ipt_entry->next_offset < ipt_entry->target_offset + ipt_target->u.target_size)
+		return -EINVAL;
+
+	rule->ipt_entry = ipt_entry;
+
+	err = init_target(ctx, ipt_target, &rule->target);
+	if (err)
+		return err;
+
+	if (rule_has_standard_target(rule)) {
+		if (XT_ALIGN(ipt_entry->target_offset +
+			     sizeof(struct bpfilter_ipt_standard_target)) != ipt_entry->next_offset)
+			return -EINVAL;
+	}
+
+	rule->num_matches = ipt_entry_num_matches(ipt_entry);
+	if (rule->num_matches < 0)
+		return rule->num_matches;
+
+	return init_rule_matches(ctx, ipt_entry, rule);
+}
+
+int gen_inline_rule(struct codegen *ctx, const struct rule *rule)
+{
+	int i, err;
+
+	const struct bpfilter_ipt_ip *ipt_ip = &rule->ipt_entry->ip;
+
+	if (!ipt_ip->src_mask && !ipt_ip->src) {
+		if (ipt_ip->invflags & IPT_INV_SRCIP)
+			return 0;
+	}
+
+	if (!ipt_ip->dst_mask && !ipt_ip->dst) {
+		if (ipt_ip->invflags & IPT_INV_DSTIP)
+			return 0;
+	}
+
+	if (ipt_ip->src_mask || ipt_ip->src) {
+		const int op = ipt_ip->invflags & IPT_INV_SRCIP ? BPF_JEQ : BPF_JNE;
+
+		EMIT(ctx, BPF_LDX_MEM(BPF_W, CODEGEN_REG_SCRATCH1, CODEGEN_REG_L3,
+				      offsetof(struct iphdr, saddr)));
+		EMIT(ctx, BPF_ALU32_IMM(BPF_AND, CODEGEN_REG_SCRATCH1, ipt_ip->src_mask));
+		EMIT_FIXUP(ctx, CODEGEN_FIXUP_NEXT_RULE,
+			   BPF_JMP_IMM(op, CODEGEN_REG_SCRATCH1, ipt_ip->src, 0));
+	}
+
+	if (ipt_ip->dst_mask || ipt_ip->dst) {
+		const int op = ipt_ip->invflags & IPT_INV_DSTIP ? BPF_JEQ : BPF_JNE;
+
+		EMIT(ctx, BPF_LDX_MEM(BPF_W, CODEGEN_REG_SCRATCH2, CODEGEN_REG_L3,
+				      offsetof(struct iphdr, daddr)));
+		EMIT(ctx, BPF_ALU32_IMM(BPF_AND, CODEGEN_REG_SCRATCH2, ipt_ip->dst_mask));
+		EMIT_FIXUP(ctx, CODEGEN_FIXUP_NEXT_RULE,
+			   BPF_JMP_IMM(op, CODEGEN_REG_SCRATCH2, ipt_ip->dst, 0));
+	}
+
+	if (ipt_ip->protocol) {
+		EMIT(ctx, BPF_LDX_MEM(BPF_B, CODEGEN_REG_SCRATCH4, CODEGEN_REG_L3,
+				      offsetof(struct iphdr, protocol)));
+		EMIT_FIXUP(ctx, CODEGEN_FIXUP_NEXT_RULE,
+			   BPF_JMP_IMM(BPF_JNE, CODEGEN_REG_SCRATCH4, ipt_ip->protocol, 0));
+
+		EMIT(ctx, BPF_LDX_MEM(BPF_B, CODEGEN_REG_SCRATCH4, CODEGEN_REG_L3,
+				      offsetof(struct iphdr, protocol)));
+		EMIT(ctx, BPF_MOV64_REG(CODEGEN_REG_L4, CODEGEN_REG_L3));
+		EMIT(ctx, BPF_LDX_MEM(BPF_B, CODEGEN_REG_SCRATCH1, CODEGEN_REG_L3, 0));
+		EMIT(ctx, BPF_ALU32_IMM(BPF_AND, CODEGEN_REG_SCRATCH1, 0x0f));
+		EMIT(ctx, BPF_ALU32_IMM(BPF_LSH, CODEGEN_REG_SCRATCH1, 2));
+		EMIT(ctx, BPF_ALU64_REG(BPF_ADD, CODEGEN_REG_L4, CODEGEN_REG_SCRATCH1));
+	}
+
+	for (i = 0; i < rule->num_matches; ++i) {
+		const struct match *match;
+
+		match = &rule->matches[i];
+		err = match->match_ops->gen_inline(ctx, match);
+		if (err)
+			return err;
+	}
+
+	EMIT_ADD_COUNTER(ctx);
+
+	err = rule->target.target_ops->gen_inline(ctx, &rule->target);
+	if (err)
+		return err;
+
+	codegen_fixup(ctx, CODEGEN_FIXUP_NEXT_RULE);
+
+	return 0;
+}
+
+void free_rule(struct rule *rule)
+{
+	free(rule->matches);
+}

@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2021 Telegram FZ-LLC
+ */
+
+#ifndef NET_BPFILTER_RULE_H
+#define NET_BPFILTER_RULE_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "target.h"
+
+struct bpfilter_ipt_entry;
+struct codegen;
+struct context;
+struct match;
+
+struct rule {
+	const struct bpfilter_ipt_entry *ipt_entry;
+	uint32_t came_from;
+	uint32_t hook_mask;
+	uint16_t num_matches;
+	struct match *matches;
+	struct target target;
+};
+
+bool rule_has_standard_target(const struct rule *rule);
+bool is_rule_unconditional(const struct rule *rule);
+int init_rule(struct context *ctx, const struct bpfilter_ipt_entry *ipt_entry, struct rule *rule);
+int gen_inline_rule(struct codegen *ctx, const struct rule *rule);
+void free_rule(struct rule *rule);
+
+#endif // NET_BPFILTER_RULE_H

@@ -4,3 +4,4 @@ test_map
 test_match
 test_xt_udp
 test_target
+test_rule

@@ -14,6 +14,7 @@ TEST_GEN_PROGS += test_map
 TEST_GEN_PROGS += test_match
 TEST_GEN_PROGS += test_xt_udp
 TEST_GEN_PROGS += test_target
+TEST_GEN_PROGS += test_rule
 
 KSFT_KHDR_INSTALL := 1
 

@@ -40,12 +41,14 @@ BPFILTER_MAP_SRCS := $(BPFILTERSRCDIR)/map-common.c
 BPFILTER_CODEGEN_SRCS := $(BPFILTERSRCDIR)/codegen.c $(BPFOBJ) -lelf -lz
 BPFILTER_MATCH_SRCS := $(BPFILTERSRCDIR)/match.c $(BPFILTERSRCDIR)/xt_udp.c
 BPFILTER_TARGET_SRCS := $(BPFILTERSRCDIR)/target.c
+BPFILTER_RULE_SRCS := $(BPFILTERSRCDIR)/rule.c
 
 BPFILTER_COMMON_SRCS := $(BPFILTERSRCDIR)/context.c
 BPFILTER_COMMON_SRCS += $(BPFILTER_MAP_SRCS) $(BPFILTER_CODEGEN_SRCS) $(BPFILTER_MATCH_SRCS)
-BPFILTER_COMMON_SRCS += $(BPFILTER_TARGET_SRCS)
+BPFILTER_COMMON_SRCS += $(BPFILTER_TARGET_SRCS) $(BPFILTER_RULE_SRCS)
 
 $(OUTPUT)/test_map: test_map.c $(BPFILTER_MAP_SRCS)
 $(OUTPUT)/test_match: test_match.c $(BPFILTER_COMMON_SRCS)
 $(OUTPUT)/test_xt_udp: test_xt_udp.c $(BPFILTER_COMMON_SRCS)
 $(OUTPUT)/test_target: test_target.c $(BPFILTER_COMMON_SRCS)
+$(OUTPUT)/test_rule: test_rule.c $(BPFILTER_COMMON_SRCS)

@@ -5,6 +5,7 @@
 
 #include <linux/bpfilter.h>
 #include <linux/netfilter/x_tables.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
 
 #include <stdint.h>
 #include <stdio.h>

@@ -39,4 +40,11 @@ static inline void init_error_target(struct xt_error_target *ipt_target, int rev
 	snprintf(ipt_target->errorname, sizeof(ipt_target->errorname), "%s", error_name);
 }
 
+static inline void init_standard_entry(struct ipt_entry *entry, __u16 matches_size)
+{
+	memset(entry, 0, sizeof(*entry));
+	entry->target_offset = sizeof(*entry) + matches_size;
+	entry->next_offset = sizeof(*entry) + matches_size + sizeof(struct xt_standard_target);
+}
+
 #endif // BPFILTER_UTIL_H

@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+
+#include "rule.h"
+
+#include <linux/bpfilter.h>
+#include <linux/err.h>
+
+#include <linux/netfilter_ipv4/ip_tables.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "../../kselftest_harness.h"
+
+#include "context.h"
+#include "rule.h"
+
+#include "bpfilter_util.h"
+
+FIXTURE(test_standard_rule)
+{
+	struct context ctx;
+	struct {
+		struct ipt_entry entry;
+		struct xt_standard_target target;
+	} entry;
+	struct rule rule;
+};
+
+FIXTURE_SETUP(test_standard_rule)
+{
+	const int verdict = BPFILTER_NF_ACCEPT;
+
+	ASSERT_EQ(create_context(&self->ctx), 0);
+	self->ctx.log_file = stderr;
+
+	init_standard_entry(&self->entry.entry, 0);
+	init_standard_target(&self->entry.target, 0, -verdict - 1);
+}
+
+FIXTURE_TEARDOWN(test_standard_rule)
+{
+	free_rule(&self->rule);
+	free_context(&self->ctx);
+}
+
+TEST_F(test_standard_rule, init)
+{
+	ASSERT_EQ(0, init_rule(&self->ctx, (const struct bpfilter_ipt_entry *)&self->entry.entry,
+			       &self->rule));
+}
+
+TEST_HARNESS_MAIN